The invention relates to an airbag system for a motor vehicle.
EP 0 812 741 A1 teaches an airbag that is deployed from a folded state into the interior of a vehicle upon inflation with a gas supplied by an inflator. Deployment of the airbag is sensed using a sensing device and the inflation process is controlled using a control device as a function of deployment sensing. To this end, in the event of a crash with an external obstacle the amount of gas fed into the airbag is controlled as a function of the sensed free path length in such a way that a reduced volume of inflation gas is introduced into the airbag.
There is provided in accordance with the present invention an airbag system for a motor vehicle comprising: a fabric airbag that is deployed upon inflation with a gas from a folded state into an interior of the vehicle; an inflation device that supplies the gas for inflating the airbag; a sensing device that senses deployment of the airbag; an electronic memory device a desired temporal and spatial deployment sequence is stored; and a control device that controls the inflation process as a function of deployment sensing, wherein the sensing device senses the temporal and spatial sequence involved in opening the folds of the airbag and compares the sensed temporal and spatial sequence to the desired temporal and spatial deployment sequence for controlling the inflation process.
The electronic memory device stores parameters that represent the unhindered temporal and spatial deployment sequence. When the deployment sequence is sensed, the sensing device supplies signals conformed to these parameters, which signals are compared with one another in the control device, which to this end comprises an appropriate comparator. Control of the deployment process then takes place as a function of the result of this comparison, wherein the amount of inflation gas supplied to the airbag may be controlled.
The measured values obtained during sensing, which represent the temporal and spatial sequence involved in unfolding the airbag folds, may for example be electrical signals for electrical resistance values. A continuous electrical conductor track may be provided on the airbag fabric, which, when the airbag is in the folded state, is short-circuited at various points, in particular at the inner and/or outer fold points of the airbag or therebetween. In the folded state a minimal electrical resistance value is present, which increases during unfolding of the airbag in accordance with the number of opened folds.
Measured values may be obtained by contactless sensing, which values represent the temporal and spatial sequence involved in opening the folds of the airbag. This may be achieved for example by one or more reflectors that are provided on the airbag.
Unfolding of the airbag may be monitored by contactless sensing, such as ultrasound, light, in particular laser, radar, infrared and other auxiliary means may be used to obtain the measured values. When detecting the reflected signals, the Doppler effect may be exploited to detect the frequency, in particular frequency variation, of the reflected signals as a measured value.
Unfolding of the airbag may be monitored by an optical fiber or an electrical conductor associated with the fabric of the airbag, wherein a signal is transmitted through this conductor during the inflation process, which signal is received at the end of the conductor. In the event of a disturbance, for example caused by a break in the conductor, the signal is absent and the gas flow is corrected, for example interrupted or stopped, as a function thereof.
Unfolding of the airbag may be monitored by pressure chambers, which are arranged on the outside of the airbag. By measuring the pressure in the respective chambers, information is obtained about the unfolding of the airbag.